Of recent years polymeric films have become a popular choice over paper for envelopes and other types of exterior packaging films which are used to protect goods from damage during transport. An example of a polymeric packaging film is TYVEK manufactured by Dupont which is a popular film used for making Federal Express envelopes. The advantages of synthetic films over paper include tear-resistance, vapor and gas barrier properties, water resistance and ease of handling in automatic machinery. One shortcoming of polymeric films, as opposed to paper, is poor printability, particularly with high speed dot matrix and thermal transfer printers. To overcome this problem, pressure sensitive paper labels which have better printability are separately prepared and affixed to polymeric packaging. However, the inconvenience and waste associated with making and using a separate label are apparent.
To improve the strength and water resistance of paper, or other non-plastics, experts have turned to a process of laminating non-plastics to various thermoplastic films which impart strength and water-resistance. Laminating is a process by which a composite, made of any one of several types of thermosetting plastics, is bonded to a non-plastic material such as paper, cloth, asbestos, wood or glass fiber. A characteristic of these laminates is high tensile and dielectric strength and low moisture absorption. Laminated papers have been particularly useful products which combine the printability of paper with the strength of plastic.
Woven and nonwoven polyolefin films which are tear-resistant and waterproof have been developed. Some of these films have been proposed as reinforcing substrates to impart tear-resistance and strength to other substrates, such as paper. An example of a woven polyolefin film is CLAF manufactured by ANCI, Amoco Nisseki CLAF, Inc. An example of a nonwoven polyolefin film is POLYSCRIM manufactured by Polybond, Inc.
The disadvantages of laminated paper include water sensitivity, lack of flame resistance, and susceptibility to biodegradation. Additionally, paper intermixed with recyclable plastic film presents serious recycling problems because they are not easily separable.
To overcome these disadvantages, plastic films have been considered. Although these films are tear resistant and water proof, they are not easily printable.
There is an increasing need for a film, particularly for packaging, which has the strength and water resistance of plastic combined with the printability of paper.
In U.S. Pat. No. 5,288,548 filed on Jul. 31, 1992, a printable polyolefin film is described for use as a label film. The film comprises a base structure which comprises a film of an olefin polymer which has on one side a blend of one or more alkylene acrylate polymers and an interpolymer of an alpha-beta monoethylenically unsaturated carboxylic acid with (i) a neutral monomeric acrylate ester and (ii) a methacrylic ester.